A review is an evaluation of a publication, product, service, or book (book review); or an event …
In addition to a critical evaluation, the review's author may assign the work a rating to indicate its relative merit. More loosely, an author may review current events, trends, or items in the news. A compilation of reviews may itself be called a review.
In a comprehensive review there is bound to be publication bias, as negative studies are less often published and the gray literature and scientific meeting abstracts are not often searched. Thirdly, recall bias is inherent to any retrospective study. Perhaps most importantly, the selection bias that is driven by complex surgical decision-making on the parts of surgeons and patients continue to play the role of confounder